• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.12 no.4
• /
• pp.273-279
• /
• 2007

In order to estimate the sedimentation rates of continental shelf and slope of Ulleung Basin in the Southwestern East Sea, $^{210}Pb,\;^{226}Ra\;and\;^{137}Cs$ were simultaneously measured by a well-type high purity germanium(HPGe) gamma detector. $^{137}Cs$ was used to determine whether the sediment were affected by bioturbation or not, and to judge the accuracy of estimated sedimentation rates. The estimated sedimentation rates decreased exponentially from slope to basin - 0.6 cm/yr in the continental shelf, $0.3{\sim}0.4$ cm/yr in the slope, and below 0.2 cm/yr in the margin of Ulleung basin. From our and other research results, we suggest followings about sediment transport of the study area. The sediment particles were transported by coastal current from south to north through the Korea Straight. And much of them were accumulated in the shelf area. And then, the rest of sediment particles were deposited in the lower slope and the southwest margin of the basin. Also the excess $^{210}Pb$ profiles indicate that the depositional processes in the study area may have been very complicate.

• Journal of the Korean earth science society
• /
• v.45 no.1
• /
• pp.72-84
• /
• 2024

Recently, the vulnerability of water resources has been increasing owing to climate change, highlighting the importance of groundwater. In particular, the Nakdong River Basin, located in the southern part of Korea, experiences frequent water scarcity phenomena, such as droughts. This study analyzed the hydrogeological characteristics of the study area by examining groundwater and stream water in the Gwangrye Stream, downstream of the Nakdong River Basin, in August and October 2023. Therefore, we collected samples from 54 groundwater wells and five streams for water quality analysis. The results of the field tests indicated an increasing trend in electrical conductivity from upstream to downstream in the study area. Laboratory analyses confirmed that the concentration of Na increased from upstream to downstream more than that of Ca. In conclusion, both stream water and groundwater were influenced by anthropogenic contamination. These changes were closely related to land use in the study area. The upstream areas are primarily composed of forests, whereas the downstream areas are composed of industrial complexes, wastewater treatment facilities, and agricultural areas, which are likely to affect both stream water and groundwater.

• Journal of Korea Water Resources Association
• /
• v.57 no.2
• /
• pp.87-97
• /
• 2024

This study analyzed the water shortage hotspot areas in South Korea using spatial clustering analysis for water shortage estimates in 2030 of the Master Plans for National Water Management. To identify the water shortage cluster areas, we used water shortage data from the past maximum drought (about 50-year return period) and performed spatial clustering analysis using Local Moran's I and Getis-Ord Gi*. The areas subject to spatial clusters of water shortage were selected using the cluster map, and the spatial characteristics of water shortage areas were verified based on the p-value and the Moran scatter plot. The results indicated that one cluster (lower Imjin River (#1023) and neighbor) in the Han River basin and two clusters (Daejeongcheon (#2403) and neighbor, Gahwacheon (#2501) and neighbor) in the Nakdong River basin were found to be the hotspot for water shortage, whereas one cluster (lower Namhan River (#1007) and neighbor) in the Han River Basin and one cluster (Byeongseongcheon (#2006) and neighbor) in the Nakdong River basin were found to be the HL area, which means the specific area have high water shortage and neighbor have low water shortage. When analyzing spatial clustering by standard watershed unit, the entire spatial clustering area satisfied 100% of the statistical criteria leading to statistically significant results. The overall results indicated that spatial clustering analysis performed using standard watersheds can resolve the variable spatial unit problem to some extent, which results in the relatively increased accuracy of spatial analysis.

• Journal of Korea Water Resources Association
• /
• v.40 no.4
• /
• pp.287-297
• /
• 2007

The procedures for identifying channel network are suggested by exploring the scaling property between the local slope and the contributing area, given that the area threshold criterion is an indispensable complement to the slope-area threshold criterion. Through the use of the above procedures and the field data, the basin slopes illustrate the trends of large scatters in space for the geomorphologic/topographic factors. According to the scaling regimes of them both the forms of landscape can be classified as topographic divergence and convergence. The presentation of the procedures proposed in this study is implemented in the case study on Seolma experimental catchment in Korea. As a result the dynamic behaviors of basin are confirmed, and thus the dynamics of channel head advance and channel network are shown to represent better than the method using the topographic chart manually.

• Journal of the Korean Geographical Society
• /
• v.33 no.1
• /
• pp.1-16
• /
• 1998

This study surveyed intensively the relationships between grain size of coarse bed materials and some principal factors in channel system, drainage area and channel slope, in Rocky Mountains. The result of this research shows that there are statistically significant relationships between these factors. Generally, the grain size and the channel slope exponentially decreased in the study area with the increase in drainage area. However, there are great differences in grain size and channel slope between upstream and downstream channels. The boundary lines are commonly located at near the mouth of canyon. From these results, it can be concluded that the bed material characteristics and the channel slope are strongly influenced by the geological and geomorphological background of the drainage basin in this study area.

• Economic and Environmental Geology
• /
• v.29 no.5
• /
• pp.561-573
• /
• 1996

The igneous rocks in the Goseong area, the southwestern part of the Gyeongsang basin, are composed of the volcanic rocks, Bulgugsa granites and intrusive andesites. The volcanic rocks are andesitic lapilli tuff, dacite and rhyolite. The granites are mainly of hornblende-biotite granite and intruded into the sedimentary basement and the volcanic rocks. The intrusion of andesitic dyke is thought to be the latest igneous activity in the area. In the variation diagrams of the major oxides, the three igneous rock types show different variational trends, indicating that they were from the different magmatic pulses. K-Ar radiometric ages suggest that the igneous activity in the Goseong area had occurred during late Cretaceous period. The ages of the volcanic rocks seem likely to have become younger due to the thermal effect by the granitic intrusion. The major element compositoinal variation of the granites from the Goseong area are compared with those from the Jindong, Geoje and Masan areas. By the comparison, it is easily understood that the Jindong granites are fairly different from the other three granites. On the other hand, the Goseong, Geoje and Masan granites generally show similar variational trends with each other, suggesting that they are of similar genetic origin. Combining the similarity of the geochemical features and the difference of the intruding ages between the Goseong and Masan granites, it seems like that the magma generation from the same source materials had occurred at a temporal interval.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.15 no.1
• /
• pp.172-183
• /
• 2012

In 2011, floods were at the worst stage of devastation in Chao Phraya river basin of Thailand. The purpose of this study is to trace the flood inundation area around Chao Phraya river basin by using Terra MODIS image because it has the ability of spatiotemporal dynamics. The MODIS indices, which included the enhanced vegetation index(EVI), land surface water index(LSWI), and the difference in the values of EVI and LSWI(DVEL), were extracted from MODIS product MOD09 8-day composite datasets with a spatial resolution of 500m from Jul. 29, 2011 to Jan. 09, 2012. We found that combined application of EVI, LSWI, and DVEL was suitable for monitoring flood inundation. For the extracted flood inundation area and water-related area. The result can be used to acquire the flood inundation data scattered and demonstrate the potential for the use of MODIS data for temporal and spatial detection of flood effects.

• Journal of Wetlands Research
• /
• v.15 no.1
• /
• pp.115-125
• /
• 2013

This study established a methodology for the application of downscaling technique in a mountainous area having large spatial variations of rainfall and tried to estimate the change of rainfall characteristics in the future under climate change using the established method. The Namhan river basin, which is in the mountainous area of the Korean peninsula, has been chosen as the study area. Artificial Neural Network - Simple Kriging with varying local means (ANN-SKlm) has been built by combining artificial neural network, which is one of the general downscaling techniques, and SKlm technique, which can reflect the geomorphologic characteristics like elevation of the study area. The evaluation of SKlm technique was done by using the monthly rainfalls at six weather stations which KMA(Korea Meteorological Administration) is managing in the basin. The ANN-SKlm technique was compared with the Thiessen technique and ordinary kriging(OK) technique. According to the evaluation result of each technique the SKlm technique showed the best result.

• Korean Journal of Remote Sensing
• /
• v.17 no.2
• /
• pp.165-181
• /
• 2001

Using a field spectrometer having a spectral range of 0.4$\mu\textrm{m}$~2.5$\mu\textrm{m}$ with a spectral resolution of 1nm, the researchers measured the reflectance of granite, andesitic rocks, sedimentary rocks, and pyrophyllite ore in the Ungsang area, Kyungsang Basin, South Korea. Spectral characteristics of the geological media were investigated from the analysis. The in-situ measured sites were selected in well exposed rock outcrops. In case of unfavorable weather conditions, rocks were sampled and remeasured under natural solar condition. The reflectance of field data was measurd at three sistes for granite, six sites for andesitic rock three sites for sedimentary rocks, and two sites for pyrophyllite ore. The vibrational absorption bands for pyrophyllite are detected in the spectral range of 2.0$\mu\textrm{m}$~2.5$\mu\textrm{m}$. The absorption band for granites in study area is not distinctive. The reflectance measured under normal field conditions showed strong absorption at wavelengths of 1.4$\mu\textrm{m}$ and 1.9$\mu\textrm{m}$ due to the effect of moisture in the atmosphere. After the bands of 1.4$\mu\textrm{m}$ and 1.9$\mu\textrm{m}$ were removed, Hull Quotient method was applied to characterize absorption bands. The reflectances of field data were calculated to estimate the band ratio corresponding to the Landsat TM and EOS Terra ASTER. The researchers suggest here that the TM band2, band3, band4, and band7 or ASTER band2, band3, band4, and band9 are the best combination for discriminating outcrops. The researchers tested and demonstrated using a Landsat TM image in the study area. For geologic applications, decorrelation stretch is also an effective tool to enhance the exposed rock mass in images.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2019.05a
• /
• pp.152-152
• /
• 2019

This study demonstrates a novel approach of remotely sensed estimates of stream flow at fifteen hydrological station in the Han River Basin, Korea. Multi-temporal data of the European Space Agency's Sentinel-1 SAR satellite from 19 January, 2015 to 25 August, 2018 is used to develop and validate the flow estimation model for each station. The flow estimation model is based on a power law relationship established between the remotely sensed surface area of water at a selected reach of the stream and the observed discharge. The satellite images were pre-processed for thermal noise, radiometric, speckle and terrain correction. The difference in SAR image brightness caused by the differences in SAR satellite look angle and atmospheric condition are corrected using the histogram matching technique. Selective area filtering is applied to identify the extent of the selected stream reach where the change in water surface area is highly sensitive to the change in stream discharge. Following this, an iterative procedure called the Optimum Threshold Classification Algorithm (OTC) is applied to the multi-temporal selective areas to extract a series of water surface areas. It is observed that the extracted water surface area and the stream discharge are related by the power law equation. A strong correlation coefficient ranging from 0.68 to 0.98 (mean=0.89) was observed for thirteen hydrological stations, while at two stations the relationship was highly affected by the hydraulic structures such as dam. It is further identified that the availability of remotely sensed data for a range of discharge conditions and the geometric properties of the selected stream reach such as the stream width and side slope influence the accuracy of the flow estimation model.